/Engine/Source/Developer/MeshMergeUtilities/Public/StaticMeshComponentAdapter.h
Adds a new material to the underlying asset/data and specify the slot names
virtual int32 AddMaterial ( [UMaterialInterface](API\Runtime\Engine\Materials\UMaterialInterface) * Material, const [FName](API\Runtime\Core\UObject\FName) & SlotName, const [FName](API\Runtime\Core\UObject\FName) & ImportedSlotName )